When a lamp including a projection lens is attached to a housing defining a lamp chamber, an error might occur in a reference position of an optical axis of the projection lens with respect to a desired specification. There is known a lamp which includes an aiming mechanism in order to eliminate this error.
The aiming mechanism includes two screws exposed to the outside of the housing. By rotating one of the screws, the reference position in the upper-lower direction of the optical axis of the lamp is adjusted. By rotating the other of the screws, the reference position in the left-right direction of the optical axis of the lamp is adjusted (e.g., see Patent Document 1).
For example, Patent Document 2 discloses a lighting device which includes a heat sink for dissipating heat generated due to light emission of a light source. In the lighting device, the heat sink is disposed outside of the housing to define a portion of a lamp chamber in which the light source is disposed, thereby enhancing the heat dissipation. This lighting device includes a screw for adjusting a reference position of an optical axis of an optical system disposed inside the lamp chamber.